Diagnostic assays and other chemical processes often require attaching a molecule to a solid support. For example, a protein is commonly attached to a solid support for an immune assay, and an oligonucleotide to a solid support for a hybridization-based assay. The attachment can be achieved in a number of different ways, including covalent bonding and non-covalent interaction. Typically, covalent attachment is more robust. See, for example, Lamture et al. (1994) Oligonucleotide Research 22: 2121–2125; Beattie et al. (1995) Mol. Biotechnol. 4: 213–225; Joos et al. (1997) Anal. Biochem 247: 96–101; Rogers et al. (1999) Anal. Biochem. 266: 23–30; and Chrisey et al. (1996) Oligonucleotide Research 24: 3031–3039.
A number of protocols have been developed to covalently attach an oligonucleotide to a support surface. One example achieves this by, e.g., synthesizing an oligonucleotide directly on a support surface using stepwise photolithographic reactions. For example, see U.S. Pat. Nos. 5,424,186; 5,510,270; and 5,744,305. Alternatively, a nucleic acid, such as a cloned cDNA, a PCR product, or a synthetic oligonucleotide, can be deposited onto a surface of a solid support, e.g., a microscopic glass slide, in the form of an array. Usually, the surface is modified in order to covalently attach a nucleic acid.